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Octal to Binary Conversion Explained: Formula, Steps & Practice

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How to Convert Octal to Binary?

The concept of convert octal to binary plays a key role in mathematics and is widely applicable to both real-life situations and exam scenarios. Understanding this conversion helps students succeed in school topics and computer basics, and is especially useful for quick number system questions in competitive exams.


What Is Convert Octal to Binary?

To convert octal to binary means changing a number from the base-8 system (octal) into the base-2 system (binary). In the octal number system, digits are 0–7, while in binary, only 0 and 1 are used. This conversion is common in topics like number system, binary number system, and computer science basics.


Key Formula for Convert Octal to Binary

Here’s the standard formula: For each digit in the octal number, write its 3-digit binary equivalent. Then, join all these groups for the final binary number.

Example: If the octal digit is 5, its binary equivalent is 101.
So, Octal Number = Each Digit’s 3-Bit Binary Equivalent Combined.
Table reference: 0₈ = 000₂, 1₈ = 001₂, ..., 7₈ = 111₂.


Cross-Disciplinary Usage

Convert octal to binary is not only useful in Maths but also plays an important role in Physics, Computer Science, and daily logical reasoning. Students preparing for JEE, Olympiad, or even school projects will see its relevance in various questions—like digital circuits or coding basics. You’ll also use this when studying the octal number system and in learning how computers store information.


Direct Method: Step-by-Step Illustration

  1. Write down the octal number. Suppose: 145₈
    Identify each digit: 1, 4, 5
  2. Find the 3-digit binary equivalent of each digit from the table below:
    1 → 001
    4 → 100
    5 → 101
  3. Write all the binary groups in order:
    1 4 5 = 001 100 101
  4. Combine for the answer:
    145₈ = 001100101₂ or simply 1100101₂

Octal to Binary Conversion Table

Octal Digit Binary Equivalent
0 000
1 001
2 010
3 011
4 100
5 101
6 110
7 111

Speed Trick or Shortcut

To convert octal to binary fast—just remember: every digit “turns into” a three-digit binary group. No need to convert to decimal first!
Tip: If you have (472)₈:
4 → 100, 7 → 111, 2 → 010. So, (472)₈ = 100111010₂. Super quick!


Indirect Method: Octal to Decimal to Binary

Sometimes, you are asked to show both the decimal and binary conversion. Here’s how to convert octal to decimal, then decimal to binary. This method is useful for checking your answer.

  1. Write the octal number. Example: 42₈
  2. Convert to decimal:
    4 × 8¹ + 2 × 8⁰ = 4 × 8 + 2 × 1 = 32 + 2 = 34
  3. Convert decimal (34) to binary:
    34 ÷ 2 = 17, remainder 0
    17 ÷ 2 = 8, remainder 1
    8 ÷ 2 = 4, remainder 0
    4 ÷ 2 = 2, remainder 0
    2 ÷ 2 = 1, remainder 0
    1 ÷ 2 = 0, remainder 1
    Now, arrange remainders in reverse: 100010₂

Thus, 42₈ = 34₁₀ = 100010₂.


Try These Yourself

  • Convert 305₈ to binary.
  • Find the binary form of 67₈.
  • Does the octal number 231₈ convert to 10011001₂? Prove your answer.
  • Try converting 52₈ to binary using both direct and indirect methods.

Frequent Errors and Misunderstandings

  • Forgetting that each octal digit needs 3 binary digits, not 1 or 2.
  • Writing two-digit binary instead of three (for example: 5 as 101, not just 01).
  • Mixing up octal to decimal and binary to octal formulas.
  • Skipping zeros at the front—leading zeros are important for accuracy in exams.

Relation to Other Concepts

The idea of convert octal to binary connects closely with topics such as binary number system and decimal number system. Mastering this helps you with base conversion problems, coding, and digital electronics.


Classroom Tip

A quick way to remember: “Each octal digit stands for 3 bits.” So, draw three boxes per digit! Vedantu’s teachers use flashcards and base conversion games to make practice fun and memorable.


We explored convert octal to binary—from definition, formula, direct and indirect methods, example problems, and common mistakes. Continue practicing with Vedantu to become confident in number system conversions and ace your Maths and Computer subjects!


Continue learning: Octal Number System Explanation | Binary Number System Basics | Decimal Number System | Number System (Full Overview)

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FAQs on Octal to Binary Conversion Explained: Formula, Steps & Practice

1. What is octal to binary conversion?

Octal to binary conversion is the process of transforming a number from the base-8 (octal) number system to the base-2 (binary) number system. This involves representing each octal digit with its equivalent 3-bit binary representation.

2. How do you convert 472 (octal) to binary?

To convert 472₈ to binary, replace each octal digit with its 3-bit binary equivalent: 4₈ = 100₂, 7₈ = 111₂, and 2₈ = 010₂. Therefore, 472₈ = 100111010₂.

3. Is there a formula for converting octal to binary?

There isn't a single algebraic formula, but a straightforward rule: Each octal digit is directly equivalent to a 3-bit binary number. Use a conversion table for quick reference.

4. Why is each octal digit represented by three binary digits?

Because 8 (the base of the octal system) is equal to 23 (the base of the binary system). This means three binary digits (bits) are needed to represent all possible values (0-7) of a single octal digit.

5. Can I convert octal to binary using a calculator or code?

Yes, many online calculators and programming languages (like Python or C) offer functions for base conversions, making octal-to-binary conversion simple and efficient.

6. What are some common mistakes to avoid when converting octal to binary?

Common mistakes include forgetting to use three bits for each octal digit, misinterpreting the binary equivalents, and not properly padding with leading zeros.

7. How can I check if my octal to binary conversion is correct?

You can verify your answer by converting the resulting binary number back to octal using grouping of 3 bits. Alternatively, convert both the original octal number and the final binary number to decimal and compare.

8. How do I convert fractional octal numbers to binary?

Convert the integer and fractional parts separately. Each octal digit before the decimal point gets converted to its 3-bit binary equivalent, as does each digit after the decimal point.

9. Does the conversion process differ for negative octal numbers?

No, the conversion process remains the same. Simply convert the magnitude of the octal number to binary and retain the negative sign.

10. What are some practical applications of octal to binary conversion?

Octal to binary conversion is crucial in computer science and digital electronics. It's used in representing data, file permissions in Unix-like systems, and understanding low-level programming concepts.

11. What is the difference between the direct and indirect methods of octal to binary conversion?

The direct method involves directly converting each octal digit to its 3-bit binary equivalent. The indirect method involves first converting the octal number to decimal, and then the decimal number to binary.

12. How can I create an octal to binary conversion table myself?

Start with the octal digits (0-7). For each digit, find its binary equivalent using successive division by 2 and noting remainders. Ensure each binary equivalent has three digits (padding with leading zeros if necessary).